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THE  EFFECT  OF  ALKALI  UPON 
PORTLAND  CEMENT 


A  DISSERTATION 

SUBMITTED  TO   THE  FACULTY 

OF   THE   OGDEN   GRADUATE   SCHOOL   OF   SCIENCE 

IN  CANDIDACY  FOR  THE  DEGREE   OF 

DOCTOR  OF  PHILOSOPHY 

DEPARTMENT  OF  CHEMISTRY 


BY 

KARL  THEODOR  STEIK 


Private  Edition,  Distributed  By 

THE  UNIVERSITY  OF  CHICAGO  LIBRARIES 

CHICAGO,  ILLINOIS 

Reprinted  from 
UNIVERSITY  OF  WYOMING  BULLETIN,  No.  122 


"dniwrsitp  of  Gbicago 


THE  EFFECT  OF  ALKALI  UPON 
PORTLAND  CEMENT 


A  DISSERTATION 

SUBMITTED   TO   THE   FACULTY 

OF    THE    OGDEN    GRADUATE    SCHOOL   OF    SCIENCE 

IN   CANDIDACY   FOR   THE   DEGREE    OF 

DOCTOR    OF   PHILOSOPHY 

DEPARTMENT  OF  CHEMISTRY 


BY 

KARL  THEODOR  STEIK 


Private  Edition,  Distributed  By 

THE  UNIVERSITY  OF  CHICAGO  LIBRARIES 

CHICAGO,  ILLINOIS 


Reprinted  from 
UNIVERSITY  OF  WYOMING  BULLETIN,  No.  122 


BULLETIN  NO.  122 


DECEMBER,  1919 


UNIVERSITY  OF  WYOMING 

AGRICULTURAL 
EXPERIMENT  STATION 


Cement  in  different  stages  of  disintegration. 

THE  EFFECT  OF  ALKALI  UPON 
PORTLAND  CEMENT— II 


Bulletins  will  be  sent  free  upon  request. 
Address :     Director  of  Experiment  Station,  Laramie,  Wyoming. 


713 


UNIVERSITY  OF  WYOMING 

Agricultural  Experiment  Station 

LARAMIE,  WYOMING 


BOARD  OF  TRUSTEES 

Officers 

ALEXANDER  B.  HAMILTON,  M.  D President 

W.  C.  DEMING,  M.  A.... .'.. Vice  President 

C.  D    SPALDING Treasurer 

F.  S.  BURRAGE,  B.  A Secretary 

Executive  Committee 

A.  B.  HAMILTON  C.  P.  ARNOLD  C.  D.  SPALDING 

Members  Term 

Appointed  Expires 

1911 .....ALEXANDER  B.  HAMILTON,  M.  D... 1923 

1911 LYMAN  H.  BROOKS .1923 

1913 CHARLES  S.  BEACH,  B.  S ! 1.  .1923 

1913 C.    D.    SPALDING. 1921 

1914. MARY   N.   BROOKS. .1925 

1915... ....... J.  M.  CAREY,  LL.  B V. 1921 

1918 .C.  P.  ARNOLD,  M.  A 1919 

1919 .  ...E.  W.  CROFT,  M.  D 1925 

1919 W.  C.  DEMING,  M.  A.. 1925 

KATHARINE  A.  MORTON,  State  Superintendent  of  Public  Instruc- 
tion  Ex  Officio 

A.  NELSON,  Ph.  D. , . .... Ex  Officio 


%       STATION  STAFF 

A.  ^NELSON,    Ph.  D. President 

A.  D.  FAVILLE,  M.  S..  . .  . . . .  .... .-".  -.-. .  . . : .  \ .....'... Director 

F.  S.   BURRAGE,  B.  A Secretary 

O.  A.  BEATH,  M.  A Research  Chemist 

C.  ELDER,  D.  V.  M Assistant  Veterinarian 

J.  C.  FITTERER,  M.  S.,  C.  E Irrigation  Engineer 

F.  A.  HAYS,  Ph.  D Associate  Animal  Husbandman 

F.  E.  HEPNER,  M.  S Research  Chemist 

J.  A.  HILL,  B.  S Wool  Specialist 

E.  H.  LEHNERT,  D.  V.  S Veterinarian 

P.  T.  MILLER,  M.  A Associate  Station  Chemist 

E.  C.  O'ROKE,  M.  A Assistant  Parasitologist 

J.  P.  POOLE,  A.  M Botanist  and  Horticulturist 

J.  L.  ROBINSON,  M.  S Assistant  Agronomist 

*J.  W.  SCOTT,  Ph.  D .  .Parasitologist 

K.  T.  STEIK,  M.  A Engineering  Chemist 

A.  F.  VASS,  Ph.  D Associate  Agronomist 

MARION  V.  HIGGINS Librarian 

F.  M.  LONG..  ..Clerk 


*On  leave. 


The  Effect  of  Alkali  Upon  Portland  Cement-II 


KARL  STEIK 


INTRODUCTION.* 

Of  the  salts  which  constitute  the  so-called  "alkali",  the  fol- 
lowing were  used  in  the  determination  of  their  effect  on  Portland 
cement:  The  sulfates  of  sodium  and  magnesium,  chlorides  of 
sodium  and  magnesium  and  the  carbonate  of  sodium.  The  nitrates 
occur  only  in  very  small  quantities  and  therefore  are  not  detri- 
mental to  any  extent  in  regard  to  the  cement  problems.  Cases 
are  mentioned  in  the  literature  where  concrete  is  supposed  to  have 
been  damaged  by  water  which  had  percolated  through  gypsum 
beds,  therefore,  effects  of  solution  of  calcium  sulphate,  too,  were 
investigated. 

In  the  Western  States  the  number  of  different  salts  present  in 
the  so-called  "alkali"  varies  according  to  local  conditions.  The 
two  most  abundant  and  frequent  salts  are  the  sulfates  of  sodium 
and  magnesium.  The  carbonate  of  sodium  is  present  in  the  black 
alkali.  The  concentration  of  the  salts  in  waters  varies  accord- 
ing to  the  localities  and  seasons  of  the  year.  Some  of  the  alkali 
lakes  are  filled  with  saturated  solutions  during  dry  seasons  and 
in  many  of  them  solid  deposits  occur  on  the  lake  bottoms. 

Experiments  were  conducted  with  solutions  of  only  one  salt 
at  different  concentrations  in  order  to  determine  the  effect  of  each 
salt  separately.  Solutions  were  also  used  which  contained  two, 
three  and  four  different  salts  at  different  concentrations.  In  order 
to  determine  the  relative  merits  in  regard  to  resisting  the  action 
of  alkali,  neat  cement  and  mortars  of  different  concentration  were 
used.  For  comparison,  several  brands  of  cement  were  tried,  but 
most  of  the  experiments  were  carried  out  on  "Ideal"  cement.  In 
all  cases  the  amount  of  solution  per  gram  of  cement  or  mortar 
was  the  same. 

Experience  showed  that  the  reaction  of  alkali  on  neat  Port- 
land cement  was  very  slow ;  consequently,  for  the  purpose  of  ob- 


*A  progress  report  on  this  problem  was  made  in  Bulletin  113  of  the  Wyoming  Station. 
Much  of  the  work  outlined  on  the  following  pages  appeared  in  the  earlier  publication  but 
is  included  at  this  time  to  round  out  and  complete  the  final  report. 


4  Wyoming  Agricultural  Experiment  Station.      Bui,  122 

taining  more  marked  results,  some  experiments  were  conducted 
with  solutions  kept  at  temperature  of  boiling  water  during  eight 
hours  a  day  for  eighteen  months.  In  connection  with  these  ex- 
periments, the  effect  of  periodical  wetting  and  drying  was  tested 
and  also  the  effect  of  treating  the  cement  with  large  quantities  of 
hot  distilled  water. 

CHEMICAL   CHANGES 

The  chemical  reactions  which  take  place  between  the  con- 
stituents of  the  alkali  were  judged  from  the  reaction  products. 
In  solutions  of  sodium  sulfate,  or  magnesium  sulfate  singly 
or  combined,  deposits  of  crystalline  calcium  sulfate  were  obtained 
as  shown  in  Figures  I  and  2.  In  dilute  solutions,  single  crystals 
were  more  likely  to  form,  as  in  Figure  i  ;  in  more  concentrated 
solutions  crystalline  rosette-like  aggregates  were  formed,  as  in 
Figure  2. 


Fig.  1. 

On  cement  kept  in  water,  crystalline  and  amorphous  deposits 
of  Ca(OH)., — calcium  hydroxide — were  obtained,  as  shown  in 
Figures  3  and  4.  The  surfaces  of  cement  kept  in  a  solution  of 
sodium  carbonate  were  either  entirely  or  partially  covered  with 
amorphous  calcium  carbonate,  CaCO;!,  as  shown  in  Figure  5. 


Dec. 


Effect  of  Alkali  Upon  Portland  Cement  —  //. 


The  magnesium  hydroxide  which  was  formed  in  solutions  of 
magnesium  sulfate  was  amorphous,  and,  usually,  mixed  with 
amorphous  calcium  sulfate.  Deposits  of  crystalline  magnesium 
hydroxide  were  obtained  on  surfaces  of  cement  kept  in  hot  solu- 
tions of  magnesium  chloride.  The  crystals  formed  small  nodules, 
as  shown  in  Figure  6. 


Wyoming  Agricultural  Experiment  Station.      Bui.  122 


Fig.  4. 


Dec.  1919     Effect  of  Alkali  Upon  Portland  Cement— II. 


Fig.  5. 


Fig.  6. 

Besides  these  products  of  reaction,  one  more  was  obtained 
from  cement  which  was  kept  in  a  5  per  cent  solution  of  sodium 
chloride.  This  solution  was  not  changed  during  the  entire  time 
of  experiments  and  the  crystals  appeared  after  a  period  of  about 
3  years.  In  other  cases,  fresh  solutions  were  used  after  each 
testing  of  the  compression  and  tension  strength  of  the  cement. 
The  crystals,  after  cleaning  off  the  adhering  matter  from  their 
surfaces,  gave  the  following  analytical  results:  SiO,,  40.14  per 


8 


Wyoming  Agricultural  Experiment  Station.      Bui.  122 


cent;  A12O3,  31.48  per  cent;  FeL,O:!,  o.n  per  cent;  CaO,  10.09 
per  cent;  'Na2O,  14.13  per  cent;  Cl,  4.32  per  cent.  Figure  7 
shows  these  crystals. 


Fig.  7. 


Dec. 


Effect  of  Alkali  Upon  Portland  Cement— II. 


From   the  above   results,   it  appears  that  the   following  re- 
actions took  place  in  different  solutions  used : 


Ca(OH)2  +  MgSO4  +  aq.  -»  CaSO4.2H2O  +  Mg(OH)2  +  aq. ; 
Ca(OH)2  +  Na2CO;t  +  aq.  -»  CaCO,  +  2NaOH  +  aq. 

The  analysis  of  the  calcium  sulfate  crystals  gave  the  follow- 
ing, showing  it  to  be  CaSO4.2H,O  :  Water,  21.0%  ;  CaO,  32.5%  ; 
SO,,,  46.3%. 

PHYSICAL  CHANGES. 

The  reaction  of  sodium  and  magnesium  sulfates  produced 
characteristic  changes,  which  were  especially  apparent  in  the  case 
of  mortars.  From  the  appearance  of  the  mortar,  it  was  possible 


Fig.  9. 


IO 


Wyoming  Agricultural  Experiment  Station.      Bui.  122 


to  tell  which  of  the  salts  had  been  acting.  Figure  8  shows  the 
cracks  formed  on  a  i  14  mortar  which  was  immersed  in  a  solution 
of  sodium  sulfate.  Notice  that  every  cu'be  in  the  set  has  been 
affected  in  the  same  manner.  In  figure  9  is  demonstrated  the 
effect  of  a  magnesium  sulfate  solution  on  T  14  mortar.  The  solu- 
tion of  sodium  sulfate  and  the  solution  of  magnesium  sulfate 
were  of  the  same  normality.  Figure  10  also  shows  the  effect  of 
magnesium  sulfate,  but  at  a  somewhat  earlier  stage  than  in  figure 
9.  The  little  clumps  of  needles  are  crystals  of  calcium  sulfate. 

As  the  concentration  of  cement  in  the  mortar  increases,  the 
cracks  appear  nearer  the  edges  of  the  briquets  and  cubes  and 
thin  layers  gradually  fall  off,  as  shown  in  figure  n.  In  figure 
12,  from  left  to  right  is  shown  a  cube  as  it  looks  when  the  first 
layer  is  nearly  off,  the  thickness  of  the  layer  and  the  cube  with 
first  layer  removed. 

Cement  which  was  immersed  in  o.  5  N.  sulfuric  acid  showed 


Fig.  10. 


Dec.  1919     Effect  of  Alkali  Upon  Portland  Cement — //. 


i  i 


the  same  kind  of  results  as  cement  in  a  solution  of  sodium  sulfate. 
In  this  experiment  the  acid  was  renewed  when  it  became  neu- 
tralized. The  effects  of  hydrochloric  acid  of  the  equivalent  con- 


12 


Wyoming  Agricultural  Experiment  Station.      Bui.  122 


centration  of  the  sulfuric  acid  used  were  somewhat  different..  In- 
stead of  parallel  cracks  produced  along  the  edges  of  cubes,  as 
•in  case  of  sulphuric  acid,  minute  cracks  in  large  numbers,  were 
produced  all  over  the  surfaces.  Figures  13  and  14  repr_esent_jhe 
results  of  the  action  of  sulfuric  and  hydrochloric  acid  respec- 
tively. 


Fij?.  13. 


Dec.  /p/p     Effect  of  Alkali  Upon  Portland  Cement — //. 


Fig.  14. 

Figure  15  shows  the  results  produced  by  the  following  treat- 
ment :  The  cubes  were  covered  with  distilled  water  and  warmed 
on  a  water-bath.  The  water  was  allowed  to  evaporate  and  the 
cement  dried.  Then  it  was  covered  with  water  again  and  the 
process  repeated.  After  a  sufficient  length  of  time  cracks  were 
formed  which  extended  from  edge  to  edge.  No  cracks  were 
formed  on  cubes  which  were  treated  in  the  same  way,  except  that 
they  were  always  covered  with  water.  Consequently  the  cracking 
was  due  to  alternate  wetting  and  drying  of  the  cement. 

In  order  to  test  the  alkali  resisting  quality  of  mortars  with 
varying  proportions  of  sand,  mortars  were  made  up  containing  as 
many  as  10  parts  of  sand  to  one  part  of  cement.  Figure  16  shows 
a  comparison  between  neat  cement  and  mortars  of  different  dilu- 
tions which  were  placed  in  a  normal  solution  of  sodium  chloride 
and  sodium  sulfate. 


14  Wyoming  Agricultural  Experiment  Station.      BuL  122 


Dec.  /p/p     Effect  of  Alkali  Upon  Portland  Cement — //.  15 

Top  row  left  to  right:  Neat  cement  in  distilled  water;  neat 
cement  which  was  heated  on  water  bath  and  was  periodically 
either  covered  with  water,  or  dry ;  the  next  ones  are  in  order : 
neat  cement ;  i  :i  ;  1:2;  1:3;  1:4;  1:5;  i  :6,  and  i  7  mortars,  all 
in  a  normal  solution  of  normal  sodium  chloride  and  sodium  sul- 
fate  for  a  period  of  6  months.  Notice  the  characteristic  cracking 
produced  by  sodium  sulfate.  All  specimens,  except  the  first  and 
third  show  the  effects  of  treatment.  The  neat  cement  in  the 
solution  looks  as  well  as  the  neat  cement  in  distilled  water. 


Fig.  17. 


1 6  Wyoming  Agricultural  Experiment  Station.      Bui.  122 

Figure  17  represents  the  effects  produced  in  a  normal  solu- 
tion of  magnesium  chloride  and  magnesium  sulfate.  Except  for 
the  first  cube  on  the  left  in  the  top  row,  which  is  neat  cement  in 
distilled  water,  the  following  cubes  from  left  to  right  had  composi- 
tions:  neat  cement;  i  :i ;  1:2;  1:3;  1:4;  1:5;  1:6;  1:7.  Dur- 
ing the  entire  period  of  6  months  the  specimens  were  not  dis- 
turbed, but  even  then  the  i  7  mortar  had  crumbled  away.  Notice 
the  bulging  which  is  characteristic  of  the  action  of  magnesium 
sulfate. 

In  figure  18  cubes  15,  17  and  19  are  i  :i,  i  :2  and  i  13  mortars 
respectively,  placed  in  a'  normal  solution  of  sodium  chloride  and 
sodium  sulfate.  Numbers  16,  18  and  20  have  the  same  respective 


Fig.  18. 

composition  as  the  ones  above,  but  these  were  in  a  normal  solu- 
tion of  magnesium  chloride  and  magnesium  sulfate,  for  a  period 
of  6  months.  Notice  how  the  cubes  in  the  solution  of  magnesium 
salts  have  expanded  and,  judging  from  appearance,  have  disinte- 
grated more.  Numbers  i  and  9  are  neat  cement  in  distilled 
water.  All  the  above  illustrations  go  to  show  that  as  the  sand 


Dec.  1919     Effect  of  Alkali  Upon  Portland  Cement-^II.  i? 

content  of  the  mortar  increases,  its  resistance  against  the  action 
of  alkali  decreases. 

Of  the  different  brands  of  cement  only  two  were  claimed  to 
be  alkali-resisting,  the  "Iron  ore"  cement,  and  the  "Alkali-proof" 
cement.  In  regard  to  the  first  one,  it  was  impossible  to  tell  from 
the  appearance  whether  or  not  it  had  been  affected.  The  first 
five  briquets  and  cubes  in  figure  19  were  made  of  "alkali-proof" 
cement.  It  is  apparent  that  a  5  per  cent  magnesium  sulfate  solu- 
tion (first)  and  a  5  per  cent  sodium  carbonate  solution  (second) 
had  some  deteriorating  effects.  Briquet  marked  59  was  coated 
with  Toch's  No.  232  R.  I.  W. ;  the  next  to  the  right  was  coated 
with  Toch's  No.  44  R.  I.  W.  This  coating  was  almost  gone  after 
24  months,  after  which  the  above  picture  was  taken. 


Fig.  19. 


CHANGES  IN  STRENGTH   OF  NEAT  CEMENT  AND  MORTARS. 

The  tables  on  the  following  pages  set  forth  clearly  some  of 
the  results  obtained  in  the  cement  investigational  work.  Addi- 
tional detailed  data  may  be  found  in  Wyoming  Bulletin  113. 


1 8  Wyoming  Agricultural  Experiment  Station.      Bui.  122 


TABLE  I — Showing  the  Average  Strength  of  Cement  Blocks  Before 


14 


SOLUTION 


Neat  Ideal  in  various  solutions: 

(1)  In  distilled  water  for  comparison. 

Distilled  water  

(2)  In  solutions   of   jingle   salts. 

(a)  7  days  in  water  before  immersion. 

Sol.  1,  NaCl,  5  per  cent 

Sol.  2,  MgSO4,   5  per  cent 

Sol.  3,  Na2S04,  1  per  cent 

Sol.  4,  Na2SO4,  5  per  cent 

Sol.  5,  Na2S04,   10  per  cent 

NaOH  5  per  cent 

(b)  14  days  in  water  before  immersion. 

Sol.  4,  Na2SO4,  5  per  cent 

Sol.  1,  NaCl,    5    per    cent 

Sol.  6,  Na2COs,  5  per  cent 

Sol.  7,  NaHCOs,  5  per  cent 

Sol.  8,  NaCl,  7  per  cent 

(c)  14    days   in   water  and    3   months   in   air   before   im>- 

mersion. 

Sol.  8,  NaCl.  1  per  cent 

Sol.  6,  Na2CO3,   5   per   cent 

(3)  Neat   Ideal  in  solutions   of   mixed   salts. 

(a)  7  days  in  water  before  immersion. 

Sol.  11,  CaClo,  MgCl,  1.33  per  cent  each 

Sol.  10,  NaCl,  Na2SO4,  MgCl2,  MgSOi,  1.25  per  cent 
each  - 

(b)  3  months  in  water  before  immersion. 

Sol.  10,   (See  No.   16) 

(c)  48  hours  in  damp  oven  before  immersion. 

Sol.  10,  NaCl,  Na2SO4,  MgCl2,  MgSO«,  1.25  per  cent 
each  

(4)  Neat  Ideal  to  show  effects  of  titn>tion. 

In  water.     Titrated   with  H2SO4* 

Sol.  14    NaCl,  Na2SO4,  2.5  per  cent  each.     Titrated 

weeklyt    

In  water.     Titrated   dailyj  

Sol.  4,  Na2SO4,  5  per  cent.     Titrated  weekly§ 


Before 
immersion 


Com- 
press 


Ibs. 
7826 


6745 

7939 
8827 
7708 
8031 
5802 

10815 
8950 
9663 
9453 

11700 


5791 
10467 


5723 
8552 
7090 

4035 


7162 
4760 
6174 


Ten- 
sion 

Ibs. 
494 


284 
664 
455 
588 
688 
594 


525 
662 
423 
437 


774 
712 


400 
337 
455 

340 
32« 

261 

387 
276 


Dec.  1919     Effect  of  Alkali  Upon  Portland  Cement — //.  19 


and  After  Being  in  Salt  Solutions  for  Various  Periods. 


After  being  in  solution: 


12  months 

24  months 

30  months 

40  months 

84  months 

Com- 
press 

Ten- 
sion 

Com- 
press 

Ten- 
sion 

Com- 
press 

Ten- 
sion 

Com- 
press 

Ten- 
sion 

Com- 
press 

Ten- 
sion 

Ibs. 

Ibs. 

Ibs. 

Jbs. 

Ibs. 

Ibs. 

Ibs. 

Ibs. 

Ibs.             Ibs. 

7145 

716 

9560 

7-15 

10907 

677 

9877 

678 

16970 

252 

9675 
11615 
10687 
8457 
11577 
8685 

994 
482 
400 
644 
660 
905 

10185 
11310 
10712 
7045 
11597 
9965 

1017 
289 
-,03 
716 
409 
920 

10452 
10030 
10282 
6482 
11265 
8515 

910 
651 
725 
701 
280 
920 

7527 
8073 
9047 
6523 
11460 
7383 

747 
612 
698 
632 
377 
768 

13057 
9472 
11742 
8525 
13887 
16107 

197 
202 
231 
297 
350 

9342 
8597 
10660 
8942 
9922 

669             5500 
905            10295 
830            10327 
847             8882 
779           11390 

297 
j-46 
717 

757 
948 

4415 

8030 
9907 
9750 
10217 

655 
762 
720 
729 
892 

5050 

10393 
12270 
9503 

455 

"685 
712 
793 

4325 

"15375  " 
10632 
16017 

305 

629  " 
220 

8740 
11540 

619 
701 

9215 

;49 

8505 
11235 

640 

672 

7950 
10833 

593 

11052 
10732 

231 
332 

7837 
11167 
10355 

336 
802 
916 

8860 
8300 

. 

7680 

844 
849 
794 

7960 
8120 

8085 

797 
745 
807 

8703 
7850 
7553 

672 
773 

860 

10147 

282 
120 
34 

5252 

10440 

297 

9880 

1105 

7325 

1131 

7920 

1175 

10100 

211 

9622 

726 

10165 

P67 

10650 

679 

10640 

255 

12570 
10240 
10522 

581 
475 
902 

11330 
10565 

9885 

876 
836 
804 

10827 
12100 
9287 

720 
821 
860 

10020 
10607 
9660 

980 
805 
740 

13380 
16600 

371 
214 

2O 


Wyoming  Agricultural  Experiment  Station.      Bui  122 


TABLE  II — Showing  Change  of  Strength  of  Cement  Blocks  During  a  Period 

Same  Cement  at  the 


1 

d 

S3 

SOLUTION 

1 

2  months 

js 

M 

«. 

Comp. 

Tens'n 

Ave. 

Comp. 

I.  Neat  Ideal  in  various  solutions: 

% 

% 

% 

% 

(1)  In  distilled  water  for  cu-mparisou. 

15 

Distilled    water 

—8.7 

+44.8 

+18.0 

+35.1 

(2)  In  solutions  of  jingle  salts. 

(a)  7  days  ?n  water  before   immersion. 

1 

Sol.  1,  NaCl,   5  per  cent 

+43.4 

+250  0 

+146  7 

+5  2 

2 

Sol.  2,  MgSO4,   5  per  cent  

+46.3 

-27  is 

+9^2 

—2.'  6 

3 

Sol.  3,  Na2SO4,  1  per  cent  

+21.0 

—12.0 

+5.5 

+0.2 

4 

Sol.  4,  .Na2SO4,  5  per  cent  

+9.7 

+9.5 

+9.6 

—16.6 

5 

Sol.  5,  Na2S04,  10  per  cent  

+44.1 

—4.0 

+20.0 

+0.2 

3S 

5   per  cent  NaOH 

+49.6 

+52.3 

+50.9 

+14.  7 

(b)  14  days  in  water  before  immersion. 

6 

Sol.  4,  Na2SO4,  5  per  cent  

—13.6 

+4.8 

—4.4 

—41.1 

7 

Sol.  1,  NaCl,    5  per   cent 

—3.9 

+72.3 

+34  2 

+19  7 

8 

Sol.  6,  Na2CO3   

+10.3 

+25.3 

+17.8 

—  3J 

9 

Sol.  7,  '\7aHCO3,  5  per  cent  

—5.4 

+100.2 

+47.4 

—0.6 

12 

Sol.  8,  NaCl,  1  per  cent 

—15.1 

+78.2 

+31.5 

+14.7 

(c)   14  days  in  water  and  3  months  in  air 

before   immersion. 

10 

Sol.  8,  NaCl,   1  per  cent  

+50.9 

—20.0 

+15.4' 

+5.4 

11 

Sol.  6,  NTa2CO3,   5  per  cent  ;  

+20.2 

—1.5 

+9.3 

(3)  Neat  Ideal  in  solutions  of  mixed  salts. 

(a)  7  days  in  water  before  immersion. 

17 

Sol.  11,  CaCl2,  Mg€l2,  NaCl,  1.33  per 

cent  each   

+36.9 

—16.0 

+10.4 

+13.0 

10 

Sol.      10,      NaCl,      Na2S04,      MgCI2, 

MgSO4,  1.25  per  cent  earn  

+30.5 

-j-137.9 

+84.2 

-25.6 

(b)  3  months  in  water  before  immersion. 

11 

Sol.      10,      NaCl,      Na2S04,      MgCl2, 

M?;S04,  1.25  per  cent  each  .'  

+46.5 

+101.3 

+73.9 

—25.7 

(c)  48    hours    in    damp    oven    before    im- 

mersion. 

33 

Sol.      10,      NaCl,      Na2S04.      MgCl2, 

M2rSO4,   1.25  per  cent  each  

4-158.7 

—12.3 

+73.2 

—5.3 

(4)  Neat  Ideal  to  show  effects  of   titration. 

37 

In  water.     Titrated  with  H2SO4*  

+81.9 

+133.7 

+107.8 

+5.6 

43 

Sol.   14,   NaCl,   Na«S04,   2.5  per  cent   each. 

Titrated    weeklyf 

+74  6 

+122  3 

+98  4 

-  -9  4 

39 

In  water.     Titrated  dailyj  

+115J 

+22^7 

+68.9 

+s!i 

15 

Sol.     4,     Na2S04,     5     per    cent.       Titrated 

weekly§     . 

+70.3 

+226.8 

+148.5 

—6.0 

*Titrated   daily;    water  changed  weekly. 
t Water  not  changed. 

tWater  changed  after  each  test  for  strength. 
iWater  changed  after  each  test  for  strength. 


Dec.  /p/p     Effect  of  Alkali  Upon  Portland  Cement — //. 


21 


in  Salt  Solutions  Expressed  as  Per  Cent,  Computed  on  the  Strength  of  the 
Last  Preceding  Test. 


After  being  in  solution: 


24  mon 
Tens'n 

ths 

30  months 

40  months 

84  months 

Ave. 

Comp. 

Tpns'n 

Ave. 

Comp. 

Tens'n 

Ave. 

Comp. 

Tens'n. 

Are. 

% 
+4.0 

+19.5 

+14.1 

—9.1 

+2.4 

—20.2 

+0.1 

—10.0 

+71.6 

—62.8 

+4.4 

+2.3 
—40.0 
+101.0 
+11.1 
—38.0 
+1.5 

+3.7 
—21.3 
+50.6 
—2.7 
—18.9 
+8.1 

+2.6 
—11.2 
—4.0 
—7.9 
—2.8 
-4.5 

—10.5 
+125.2 
—10.0 
—2.0 
—31.5 
0 

—3.9 
+57.0 
—7.0 
—4.9 
—17.1 
—2.2 

—27.9 
—19.5 
—11.9 
-J-0.6 
—7.1 
-15.3 

—16.8 
—5.9 
—3.7 

—9.8 
+34.6 
—16.5 

—22.3 
—20.9 
—7.8 
—4.6 
+13.7 
—15.9 

+73.4 
+17.2 
+29.7 
+30.6 
+21.1 
-118.1 

—73.8 
—66.9 
—66.9 
—53.0 
—7.1 

—0.1 

—29.8 
—18.6 
—11.2 

+7.0 

—55.6 
—6.5 
—13.6 
—10.6 
+21.6 

—48.3     —19.7 
+6.6li   —22.0 
—8.3  ||     —4.0 
—5.6       +9.7 
+18.6      —10.2 
I 

+123.9 
—9.9 
+0.4 
—3.7 
—5.9 

+52.1 
—15.8 
—1.8 
+3.0 
—8.0 

+14.3 

—30.5 

—8.1 

—14.3 

—33.6 

—33.6 

+4.9 
+25.8 
—6.9 

—4.8 
—2.3 
—11.1 

0 
+11.7 
—9.0 

+47.3 
—13.3 

+68.5 

—72  '.2 

•™— 

—1.8 

+21.0 

+13.2 

-7.7 
—2.6 

—14.5 
—4.1 

—11.1 
—3.3 

—6.5 
—5.3 

—7.3 
—18.1 

—6.9 
—11.7 

+39.2 
+5.9 

—61.0 
—31.6 

—0.9 
—18.3 

+151.1 

+82.0 

—10.0 

—5.5 

—11.8 

+8.5 

—15.6 

—3.5 

+20.0 

—58.0 

—19.0 

—5.8 

—9.9 

—2.1 

—12.2 

—7.7 

—3.3 

+3.7 

+0.2 

—84.4 

—13.3 

—19.5 

+5.2 

•H.i 

+3.4 

—6.5 

+6.5 

0 

—23.4 

—18.0 

—36.3 

+272.0 
—12.4 

+.50.7 
+76.0 

—10.8 

+133.3 
—3.9 

+20.6 
+34.5 

—8.4 

—5.6 

+4.7 

—4.4 

+14.4 

—6.0 

+2.3 
+1.7 

—17.8 
—1.7 

+6.9 

—1.6 
+3.2 

—11.1 
+6.3 

+0.4 

+8.1 
—0.1 

—7.4 
—12.3 

+4.0 

+3.9 
—62.4 

+22.2 
—1.9 

—13.9 

+6.0 
—31.2 

+7.4 
—7.1 

—4.9 

+27.5 

—82.0 

—27.2 

+33.5 

+56.5 

&L' 

—62.1 
—73.4 

—  w'.s 

—8.4 

22 


Wyoming  Agricultural  Experiment  Station.      Bui.  122 


TABLE   III — Showing   the  Strength   of  Cement  Blocks  Before  and  After 

of  Cement  Blocks  in  Water 


Lab  No. 

SOLUTION 

Before  Immersion 

12 

d 

.U 

Tension 

Average 

d 

S 

0 

O 

15 

1 

2 
3 
4 
5 

38 

6 
7 
8 

9 
12 

10 
11 

17 
16 

14 

33 

37 
43 

39 
45 

I.  Neat  Ideal  in  various  solutions: 
(1)  In  distilled  water  for  comparison. 
Neat  Ideal.     In  distilled  water  
(2)  In  solutions  of  single  salts, 
(a)  7  days  in  water  before  immersion. 
Sol.  1,  NaCl,  5  per  cent  

% 
100 

86.1 
101.4 
112.7 
98.4 
102.6 
74.1 

138.1 
114.2 
123.5 
120.8 
149.5 

74*0 
133.7 

73.1 
109.3 

90.6 

51.6 
65.0 

91.5 

68.2 

78.8 

% 
100 

57.4 
134.4 
92.1 
119.0 
139.2 
120.2 

129.1 
106.3 
134.0 
85.6 
95.7 

156.7 
144.1 

81.0 
68.2 

92.1 

68.8 
66.0 

52.8 
78.3 

55.8 

% 
100 

71.7 
117.9 
102.4 
108.7 
120.9 
97.1 

133.6 
110.2 
128.8 
108.2 
122.6 

115.3 
138.9 

77.0 
88.7 

91.3 

60.2 
65.5 

72.1 
73.2 

67.3 

% 
100 

135.4 
162.5 
149.5 
118.0 
162.2 
121.5 

130.7 
120.3 
149.2 
125.4 
138.8 

122.3 
161.5 

109.6 
156.1 

144.9 

146.1 
134.6 

175.0 
143.3 

147.1 

Sol    2,  MgSO4,   5  per   cent 

Sol.  3,  Na2SO4,  1  per  cent  
Sol    4    Na2SO4    5  per  cent 

Sol.  5,  Na2SO4,  10  per  cent  
5  per  cent  NaOH 

(b)  14  days  in  water  before  immersion. 
Sol.  4,  Na2SO4,  5  per  cent  
Sol    1,  NaCl,  5  per  cent 

Sol.  6,  Na->CO3,  5  per  cent  
Sol.  7,  NaHCO3,  5  per  cent  

Sol    8    NaCl    1  per  cent 

(c)  14  days  in  water  and  3  months  in  air  before 
immersion. 
Sol.  8,  NaCl,  1  per  cent  
Sol.  6,  Na2CO3,  1  per  cent  
(3)  Neat  Ideal  in  solutions  of  mixed  salts, 
(a)  7  days   in  water  before   immersion. 
Sol.  11,  CaCl2,    MgCl2,    NaCl,    1.33    per  cent 
each     
Sol.  10,  NaCl,    Na2S04,    MgCl2,   MgSO4,    1.25 
per  cent   each 

(b)  3  months  in  water  before   immersion. 
Sol.  10,  NaCl,    Na2S04,   MgCl2,    MgSO4,    1.25 
per  cent  each 

(c)  48  hours  in  damp  oven  before  immersion. 
Sol.  10,  NaCl,    Na2SO4,    MgCl2,    MgSO4,    1.25 
per  cent  each  
(4)   Neat  Ideal  to  show  effects  of  titration. 
In  water.     Titrated  daily  with  HoSO4*  
Sol.  14,  NaCl,  Na2SO4,  2.5  per  cent  each.    Titrated 
weeklv    with    H2SO4f 

In  water.     Titrated  daily  with  H2SO4J  
Sol.  4,  Na2SO4,  5  per  cent.     Titrated  weekly  with 
H2S04t    

*Water  changed  weekly. 
tSolution  not  changed. 
$Water  changed  after  each  test  for  strength. 


Dec.  1919     Effect  of  Alkali  Upon  Portland  Cement — //. 


Given  Periods  in  Salt  Solutions  Expressed  as  Per  Cent  of  the  Strength 
for  a  Similar  Length  of  Time. 

After  being  in  solution: 


month 

1 

z 

d 

s 

24  months 

30  months 

40  months 

84  months 

a 

£ 

0 

jt 

1 

\\ 

a 
£ 

0 

a 

o 

1 

1 

i 

a 
£ 
o 

3 

5 

I 

a 
I 

o 
a 
d 
9 

EH 

tt 

C3 

—  :  



° 

"£ 

~ 





— 







100 

100 

100        100 

100 

100 

100 

100 

100 

100 

100 

100 

too 

100 

138.8 
67.3 
55.8 
89.9 
92.1 
126.3 

93.4 
126.3 
115.9 
118.2 
108.8 

137.1 
114.9 
102.6 
103.9 
127.1 
123.9 

112.0 
122.3 
132.5 
121.8 
123.8 

106.5 
118.3 
112.0 
73.6 
121.3 
104.2 

57.5 

136.5 
38.7 
108.1 
96.1 
54.9 
123.4 

39.8 

121.5 

78.5 
110.0 
84.9 
83.1 
113.8 

48.6 

95.8 
91.9 
94.2 
59.4 
103.2 
80.8 

40.5 

134.4 
96.1 
107.0 
103.5 
41.3 
35.8 

96.7 

115.1 

94.0 
100.6 
81.4 
72.2 
103.3 

68.6 

76.2 

81.7 
91.6 
66.0 
105.8 
74.7 

51.1 

110.1 
90.2 
102.9 
93.1 
55.6 
113.2 

67.1 

93.1 

85.9 
97.2 
79.5 
80.7 
93.1 

59.1 

76.8 
55.7 
69.1 
50.2 
81.8 
94.9 

25.4 

78.1 
80.1 
91.6 
117.8 
138.9 

121.0 

77.8 
67.9 
80.3 
84.0 
110.3 

73.2 

107.7 
108.0 
92.9 
t!9.1 

113.5 
96.2 
101.6 
127.2 

110.6 
102.1 
97.2 
123.1 

73.6 
90.8 
89.3 
93.6 

112.5 
106.3 
107.6 
131.7 

93.0 
98.5 
98.4 
112.6 

105.2 
124.2 
96.2 

100.2 
105.0 
116.9 

102.6 
114.6 
106.5 

90.5 
62.6 
94.3 

249.6 
87.3 

156.1 
90.8 

186.4 
97.8 

104.3 
129.6 

96.3 

100.5 


98.4 

77.9 
103.0 

94.5 
99.2 

86.2 
101.  1 

80.4 
107.6 

87.4 
81.1 

83.7 
94.3 

65.1 
63.2 

91.6 
131.7 

78.3 
97.4 

46.9 

78.2 

92.6 

119.9 

102.2 

72.9 

117.7 

95.3 

88.1 

99.1 

93.6 

61.5 

111.9 

86.7 

112.0 

134.0 

86.9 

113.9 

100.4 

74.4 

110.0 

92.2 

79.4 

114.0 

96.7 

47.6 



127.9 

136.4 

80.3 

106.5 

93.4 

74.1 

119.2 

91.6 

76.4 

126.8 

101.6 

34.7 

13.1 

23.9 

41.4 

93.7 

103.3 

148.3 

120.8 

67.1 

167.0 

117.0 

80.1 

174.7 

122.4 

59.5 

83.7 

71.6 

101.3 

117.9 

106.3 

89.5 

97.9 

97.1 

102.2 

98.6 

107.7 

37.6 

72.6 



81.1 
66.2 

125.9 

123.0 
104.7 

136.5 

118.5 
101.5 

103.3 

117.5 
112.2 

107.9 

118.0 
111.3 

105.6 

99.3 
110.9 

84.3 

106.3 
121.2 

127.0 

102.3 
116.0 

105.6 

101.4 
107.3 

97.8 

144.5 
118.7 

109.1 

122.9 
113.0 

103.4 

78.8 
97.8 

147.2 
84.9 

113.0 
91.3 

Wyoming  Agricultural  Experiment  Station.      Bui.  122 


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Dec.  1910     Effect  of  Alkali  Upon  Portland  Cement — 77. 


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Dec.  1919     Effect  of  Alkali  Upon  Portland  Cement— II.  29 

DISCUSSION   OF   THE  DATA. 

The  chief  reacting  substance  in  the  cement  is  lime,  in  the 
form  of  calcium  hydroxide.  It  may  be  formed  either  from  the 
hydration  of  the  calcium  oxide  present  in  the  clinker,  or  may  be 
formed  during  the  setting  of  cement.  With  the  sulfate  salts  of 
sodium  and  magnesium  it  forms  calcium  sulfate,  CaSO4.2H2O, 
and  sodium  hydroxide  with  the  former  and  magnesium  hydroxide 
with  the  latter.  The  ratio  of  the  molecular  volume  of  calcium 
sulfate  formed  in  the  reaction  to  the  molecular  volume  of  calcium 
hydroxide  is  as  1.98:1.  The  sodium  hydroxide  formed  in  re- 
action with  sodium  sulfate  remains  in  solution.  In  the  case  of 
magnesium  sulfate,  the  ratio  of  the  molecular  volume  of  calcium 
sulphate,  plus  the  magnesium  hydroxide  formed  in  the  reaction  to 
the  molecular  volume  of  calcium  hydroxide  originally  in  the 
cement  is  as  2.78:1.  In  Bulletin  81  of  Montana  Experiment  Sta- 
tion, the  disintegration  of  cement  is  ascribed  as  being  due  to  this 
formation  of  compounds  with  larger  molecular  volumes,  causing 
expansion  and  consequent  cracking.  Another  theory,  similar  to 
the  above,  is  held  by  several  experimenters.  According  to  this 
theory,  tricalcium-aluminium  sulfate  is  formed,  and  this  then 
causes  the  expansion  and  disintegration  of  cement.  In  Tech- 
nologic Paper  No.  12  of  the  Bureau  of  Standards,  by  Messrs. 
Bates,  Phillips,  and  Wig,  data  is  produced  to  disprove  this 
theory. 

Turning  to  the  data  given  in  tables  i  and  2,  based  on  an 
84  month  period  of  action,  we  find  that  the  changes  in  com- 
pression strength  and  changes  in  tension  strength  do  not  always 
go  parallel ;  one  may  increase  while  the  other  may  decrease, 
and  vice  versa.  The  5%  solution  of  sodium  sulfate  affected 
the  compression  strength  more  than  any  other  solution  of  one 
salt  only,  cement  thus  treated  having  only  25.4%  of  the  com- 
pression strength  of  cement  in  distilled  water  for  the  same 
length  of  time.  The  next  lowest  compression  strength  was  shown 
by  cement  in  following  solutions:  Magnesium  sulfate  (557%)> 
sodium  bicarbonate  (62.6%),  sodium  chloride  (76.8%),  and 
sodium  carbonate  (90.5%).  The  solution  of  sodium  sulfate  was 
used  in  3  different  concentrations:  i%,  5%  and  10%,  and  the 
compression  strength  of  cement  kept  in  these  solutions  was  69.1%, 


30  Wyoming  Agricultural  Experiment  Station.      Bui.  122 

$0.2%  and  81.8%  respectively  at  the  end  of  84  months.  It  also 
appears  that  cement  which  has  been  in  ordinary  or  distilled  water 
for  a  longer  period  was  affected  more  strongly,  thus  cement  14 
days  in  water  before  immersion  in  a  5%  solution  of  sodium  sul- 
fate  only  had  a  compression  strength  equal  to  25.4%. 

It  is  a  noticeable  fact  that  the  compression  strength  after  84 
months  is  rather  high  in  most  cases,  but  that  the  tension  strength 
is  low,  even  for  cement  which  was  kept  in  distilled  wrater.  On 
the  average,  it  is  only  50  per  cent  of  the  tension  strength  which 
the  cement  had  before  immersion.  This  difference  between  com- 
pression and  tension  strength  becomes  more  noticeable  when 
considering  the  effects  of  solutions  which  contained  more  than 
one  salt.  In  the  case  of  solution  No.  10,  which  contained  the 
sulfates  and  chlorides  of  sodium  and  magnesium,  when  the  ten- 
sion strength  of  cement,  which  was  in  water  14  days  and  3  months 
before  immersion  in  solution,  was  only  120  and  34  Ibs.  respective- 
ly. The  tension  strength  of  cement  which  was  only  48  hours  in 
a  damp  oven  before  immersion  in  solution  No.  10  at  the  end  of 
84  months  still  was  211  Ibs.,  thus  showing  again  that  younger 
cement  is  less  affected. 

The  compression  and  tension  strength  of  cement  in  different 
sets  recorded  in  the  table  was  not  the  same  for  all  sets  before 
immersion  in  solutions.  Regardless  of  what  the  strength  was 
before  immersion,  in  all  cases  the  maximum  was  reached  some- 
time during  the  experiment,  and  this  maximum  is  very  nearly  the 
same.  In  every  case  recorded,  even  in  the  case  of  cement  which 
was  in  water  3  months  previous  to  immersion  in  a  solution,  the 
compression  as  well  as  the  tension  strength  always  increased  after 
the  immersion  in  a  solution  until  the  maximum  was  reached.  If 
the  formation  of  molecules  which  have  larger  volumes  than  the 
original  compounds  of  set  cement  is  the  cause  of  the  disintegration 
of  cement,  then  this  would  be  more  pronounced  soon  after  im- 
mersion, for  then  the  formation  of  CaSO.4.2H2O  would  be  faster 
than  it  would  be  later.  Consequently,  the  decrease  of  strength 
should  be  most  noticeable  during  the  reaction.  The  tacts  do  not 
show  this  to  be  true.  The  progress  of  the  formation  of  hydrated 
calcium  sulfate  from  lime  and  sodium  sulfate  can  be  followed  by 
determining  the  amount  of  sodium  hydroxide  formed  in  the  re- 


Dec.  1919     Effect  of  Alkali  Upon  Portland  Cement — //.  31 

action.  This  was  done  by  titrating  the  solution  to  neutral  with 
sulfuric  acid.  The  procedure  was  carried  on  until  no  more 
sodium  hydroxide  was  formed,  which  was  after  24  months.  At 
this  time  the  cement  should  be  the  weakest.  Figure  20  represents 
graphically  the  change  of  compression  strength  and  the  amount 
of  acid  required  to  neutralize  the  sodium  hydroxide  formed,  the 
neutralizing  being  done  every  day.  Instead  of  the  expected  de- 
crease of  strength  during  this  reaction,  there  was  an  increase. 


Fig.  20. 

Besides,  the  cement  in  magnesium  sulfate  solution  should  have 
a  lower  strength  than  cement  in  sodium  sulfate  solution.  The 
results  show  that  this  is  not  the  case.  This  does  not  mean  that 
the  formation  of  reaction  products,  which  have  larger  molecular 
volumes  than  the  reagents  in  the  cement,  does  not  contribute 
towards  disintegration.  But  it  is  not  the  chief  cause  or  the  only 
cause  of  disintegration. 

In  tables  6,  7  and  8  are  given  the  strength  values  of  cement 
kept  in  solution  at  the  temperature  of  boiling  water.     The  results 


32  Wyoming  Agricultural  Experiment  Station.      Bui.  122 

after  a  period  of  18  months  are  characteristic.  The  set  which  was 
completely  disintegrated  is  the  one  which  was  in  a  solution  of 
magnesium  chloride,  while  the  cement  in  a  solution  of  magnesium 
sulfate  had  an  average  compression  strength  of  9775  Ibs.,  and 
cement  in  a  solution  of  sodium  sulfate,  6122  Ibs.  Noteworthy  is 
the  fact  that  cement  kept  in  solution  containing  both  magnesium 
chloride  and  sulfate  still  had  a  strength  of  2365  Ibs.,  and  cement 
in  a  solution  containing  magnesium  sulfate  and  sodium  chloride, 
4797  Ibs.  Evidently  the  solution  of  sodium  chloride  did  not  pro- 
duce any  bad  effect,  since  the  strength  of  cement  in  it  was  12735 
Ibs.,  while  the  strength  in  hot  distilled  water  was  only  10922  Ibs. 
These  results  suggest  the  following  questions:  Why  did  mag- 
nesium chloride  have  the  strongest  disintegrating  effect?  Why 
did  the  solution  of  magnesium  chloride  containing  also  magnesium 
sulfate  produce  a  slower  decrease  in  strength  than  the  solution 
containing  magnesium  chloride  alone  ?  Why  was  the  strength  of 
cement  kept  in  the  solution  of  magnesium  sulfate  containing  also 
sodium  chloride  50  per  cent  less  than  the  strength  of  cement  in  the 
solution  of  magnesium  sulfate  alone,  although  the  solution  of 
sodium  chloride  did  not  produce  any  bad  effects  ? 

The  answer  to  the  first  question  is  the  fact  that  magnesium 
chloride  in  solution  undergoes  hydrolysis,  the  result  of  which  is 
the  formation  of  hydrochloric  acid.  It  is  then  this  hydrochloric 
acid  which  attacks  the  cement.  The  hydrolysis  of  magnesium 
chloride  in  solution  goes  on  to  a  lesser  extent  when  magnesium 
sulfate  is  also  present  in  solution.  For  this  reason  the  disinte- 
grating effect  of  a  solution  containing  both  salts  is  less  severe  for 
equal  periods. 

When  magnesium  sulfate  and  sodium  chloride  are  dissolved 
together  in  water,  the  solution  contains  4  salts  instead  of  two. 
This  may  be  expressed  by  the  following  equation:  MgSO4+ 
2Na€l*=$MgCl2+ Na,SO4.  The  magnesium  chloride  thus  pro- 
duced hydrolizes  and  the  result  of  this  reaction  is  the  formation 
of  hydrochloric  acid:  MgCl2+H2O±?Mg(OH)2+HCl.  As  the 
dydrochloric  acid  reacts  with  the  components  of  the  cement,  it  is 
being  removed,  so  to  speak,  and  the  result  of  this  is  that  the  above 
reactions  gradually  progress  toward  the  right. 


Dec.  1919     Effect  of  Alkali  Upon  Portland  Cement — //.  33 

Results  analogous  to  those  obtained  in  hot  solutions  were 
also  obtained  from  experiments  on  mortars  with  various  propor- 
tions of  sand.  Again,  the  magnesium  chloride  solution  had  the 
most  rapid  disintegrating  effect  and  other  solutions  in  the  same 
order  as  above.  But  the  results  in  this  table  show  also  that  as 
the  proportion  of  sand  in  the  mortar  increases  the  disintegration 
is  hastened.  The  data  in  these  tables  are  in  agreement  with  con- 
clusions from  figures  16,  17  and  18.  Although  for  numbers  60, 
61  and  62  the  strength  after  18  months  in  solution  is  higher  than 
the  strength  which  the  mortars  had  before  immersion,  neverthe- 
less there  is  a  decided  decrease  of  strength  after  the  maximum 
had  been  reached. 

The  data  recorded  in  table  9  were  meant  to  give  a  compari- 
son of  the  resistance  to  action  of  alkali  by  i  :i  mortars  prepared 
with  cements  of  different  brands.  The  comparison  of  sets  22 
and  23  is  interesting.  Apparently  the  presence  of  sodium  car- 
bonate in  the  solution  counteracted  the  disintegrating  effect.  No. 
22  in  a  solution  containing  sodium  carbonate,  sulfate  and  chloride 
after  84  months  had  higher  compression  strength  (11830  Ibs.) 
than  the  cement  No.  60  in  solution  of  sodium  chloride  and  sulfate 
had,  after  18  months  (7612  Ibs).  The  same  is  also  true  for 
tensile  strength.  These  results  are  graphically  represented  in 
figures  21  and  22  for  compression  and  tension  strength  respec- 
tively. 

The  cements,  of  brands  tried,  do  not  show  very  much  differ- 
ence in  compression  strength.  The  "Alkali-proof"  cement  had  the 
lowest  compression,  below  normal,  while  the  others  did  not  show 
any  decrease.  The  tensile  strength  of  all  of  them,  although  still 
higher  than  the  tensile  strength  of  cement  in  distilled  water,  show 
distinctly  a  decrease  after  the  maximum  had  been  reached.  It  is 
noteworthy  that  the  cements  which  were  made  up  with  solutions 
of  sulfuric  acid  of  various  concentrations  and  also  kept  in  the 
above  solution  (containing  sodium  carbonate,  sulfate  and  chlo- 
ride) had  normal  compression  strength,  but  the  tensile  strength 
also  had  decreased  during  the  last  period.  The  cement  which 
w^s  mixed  with  a  solution  containing  one  per  cent  of  sulfuric 
acid  and  di-sodium-hydrogen  phosphate,  at  the  end  of  84  months 
in  the  above  solution  had  normal  compression  strength  and  the 


34 


yoming  Agricultural  £.r/>m"iwrwf  Station.     Bnl.  122 


Fig.  21. 


/  -TUT-    tt«^ 

^  B».  ^  <wl  not 


The 


it  is  snfc  204 
i0r  vixiocr  op 


*•  ^ 

54 

&  53,  54 


-        - 


Effect  of  Alkali  Upon  Portland  CYimW—  //.  35 

a  solution  was  used  for  mixing  which  contained  an  organic  sub- 
stance, a  distinctly  inferior  cement  was  obtained.  The  results  with 
the  "  Alkali-proof"  cement  are  represented  in  table  10.  It  is  evi- 
dent that  its  tensile  strength  suffered  greatly  after  the  maximum 
had  been  reached,  regardless  of  what  the  solution  was.  Here,  too, 
a  comparison  between  the  results  in  this  table  and  No.  51  in  table 
9  distinctly  show  that  the  solution  which  contained  sodium  car- 

.ie  was  less  harmful. 

For  testing  out  the  value  as  surface  protectors  against  the 
action  of  alkali  of  different  commercial  paints  recommended  as 
waterproofers,  t  :^  mortar  was  covered  with  them.  The  mortar 
of  each  set  received  2  coatings  of  some  one  paint.  After  24 
months  in  a  solution  of  sodium  carfaonate-sul  fate-chloride  the 
paints  were  off.  Tint  the  paints  after  that  did  no*  offer  resist- 
ance to  penetration  of  solutions  is  shown  by  the  marked  dyf^my 
of  tensile  strength  during  the  last  period  of  60  months.  Although 
ico  C  paint  was  off  after  12  months,  some  of  the  "yfl^K 
of  the  paint  must  have  had  a  beneficial  effect  as  ptoteclofs,  since 
in  this  even  the  tensile  strength  did  not  decrease  liming  the  las* 
period  of  50  months. 

In  actual  practice  cement  fuequently  is  only  periodically  ex- 
posed to  the  action  of  alkali.  This  change  of  conditions  from 
wet  and  dry  itself  has  a  deteriorating  effect  on  the  cement.  in 
set  Ho.  ?i  the  cement  was  periodically  wet  and  dry  and  the  result 
was  that  its  compression  strength  was  2$%  less  than  that  off 
cement  which  was  under  water  constantly.  Ttae  solvent  effect  of 
large  volumes  of  water  also  conies  in  pb\\  as  seen  Iran  No,  72, 
This  cement  was  trailed  with  3  liters  of  *i^  distilled  water  even? 
day  daring  a  period  of  i&  months  and  the  result  is  uhat  its  com- 
pression strength  at  the  end  of  tthiis  period  was  3*-$%  less  than 
the  compression  strength  of  cement  which  was  undtef  the 
conditbr-  >i  nhat  the  water  never  was  cliinffji.  In 

the  dismtegration  of  cement  is  Kne  result  of  aH  the 
causes  combined,  and  besides  it  is  aocetetmled  %  fimjung  and 


The  entire  prooectare  mqjMt  he  described  as  Mows;    Ce- 

.  .  .;    .!   i  '  !   ..  :  ,  v    ..^c      v\  !:;    .   .  .  •;     .  .  v,  :.::  ,  ..  ,v   ,   ;    s;4  ;:>    .   ;       ,.,^,  io  ...; 

as  a  rofe,  shows  an  increase  of  jJuenfUh,  Tins 


36  Wyoming  Agricultural  Experiment  Station.      Bui.  122 

until  a  maximum  is  reached.  During  this  period  the  reaction 
between  the  salts  and  the  calcium  hydroxide  takes  place  and  if 
any  bad  effects  are  produced  from  these  reactions,  they  are  not 
marked  by  a  decrease  in  the  strength  of  the  cement.  The  cause  of 
this  may  be  that  the  increase  in  strength  during  this  period  is 
greater  than  the  decrease.  The  calcium  sulfate  or  calcium  car- 
bonate, as  the  case  may  be,  increases  the  density  of  cement  and 
makes  it  less  pervious  to  the  solutions.  Besides,  the  calcium  sul- 
fate has  a  binding  value,  which  may  reach  200-300  Ibs.  This  was 
tried  out  on  halves  of  a  broken  briquet ;  they  were  cemented  to- 
gether and  it  took  that  much  force  to  full  them  apart.  When  the 
compounds  of  the  cement  other  than  the  calcium  hydroxide  are 
attacked,  then  the  decrease  of  strength  begins  to  show.  As  the 
table  of  analyses  shows,  the  extent  of  chemical  changes  is  com- 
paratively small.  What  the  changes  may  be  can  to  some  extent 
be  judged  from  the  analysis  of  the  crystals  shown  in  figure  7. 
The  effect  of  magnesium  chloride  is  more  marked  than  the  effect 
of  the  other  salts  because  the  hydrochloric  acid  formed  due  to 
hydrolysis  reacts  with  the  fundamental  compounds  of  cement. 
In  the  case  of  chlorides,  the  calcium  chloride  formed  is  removed 
from  the  cement,  while  in  the  case  of  sulfates,  the  calcium  sulfate 
is  deposited.  The  experiments  with  equivalent  solutions  of  hydro- 
chloric and  sulfuric  acids  show  that  the  former  is  more  harmful. 
After  6  months  the  strength  of  cement  in  hydrochloric  acid  de- 
creased 22%,  in  sulphuric  acid  only  16%.  The  difference  may 
be  due  to  the  fact  that  the  calcium  sulfate  formed  makes  the 
cement  less  permeable.  That  the  mortars  are  more  rapidly  de- 
stroyed than  the  neat  cement  is  to  be  expected.  For  the  same 
jweight,  they  contain  less  of  the  reacting  material,  but  expose  as 
much  surface  to  the  action  of  solutions  as  neat  cement.  Conse- 
quently, a  greater  proportion  of  their  cement  content  has  been 
jreached  in  shorter  time.  The  effects  from  the  reactions  are 
augmented  by  the  dissolving  action  which  increases  the  porosity 
of  cement,  by  the  friction  of  particles  carried  in  suspension,  by 
the  wearing  away  of  the  weakened  surface  layers,  thus  exposing 
deeper  layers  of  cement,  and,  finally,  by  the  formation  of  cracks 
due  to  uneven  expansion  and  contraction,  through  which  the  solu- 
tion also  penetrates  deeper  into  the  cement.  Any  process  which 


Dec.  ip/p     Effect  of  Alkali  Upon  Portland  Cement — //.  37 

will  make  the  cement  less  porous  and  less  permeable  to  the  solu4 
tions  will  also  increase  its  resistance  to  the  action  of  alkali.  In 
this  connection,  attention  may  be  called  to  the  behavior  of  cement 
which  was  not  mixed  with  water  but  with  solutions  containing 
ions  forming  insoluble  calcium  salts.  Results  with  oxalic  acid 
(5%)  used  for  mixing  the  cement  and  which,  after  setting,  was 
put  in  a  hot  solution  of  N.  sodium  sulfate  and  N.  sodium  chlo- 
ride were  as  follows :  Compression  strength  before  immersion, 
8502 ;  after  6  months  in  solution,  10742 ;  after  12  months,  10280, 
and  after  18  months,  13685  Ibs.  Cement  mixed  with  a  solution  of 
magnesium  flouride  had  a  compression  strength  before  immersion 
6087  Ibs ;  after  6  months  in  the  above  sodium-chloride-sulfate 
solution,  9499  Ibs.,  and  after  18  months,  15580.  Since  these  sub- 
sta'nces  and  also  the  sodium  phosphate  and  sulfuric  acid  are  not 
very  expensive,  their  solutions  could  be  used  in  cement  practice. 

The  results  with  a  hot  saturated  calcium  sulfate  solution  are 
not  recorded  in  the  tables.  The  compression  strength  of  cement 
varied  as  follows:  Before  immersion,  7240;  after  6  months, 
9452;  12  months,  8745  ;  18  months,  11710. 

Evidently  the  calcium  sulfate  solution  did  not  have  any  bad 
effect  upon  the  strength  of  cement. 


38  Wyoming  Agricultural  Experiment  Station.      Bui.  122 

SUMMARY 

Cement  put  in  solutions  of  salts  which  constitute  the  "alkali" 
sets  as  well  as  in  water. 

In  solutions  of  sodium  sulfate,  or  magnesium  sulfate  CaSO4. 
2H.,O  is  formed  and  NaOH  and  Mg(OH)a  respectively. 

A  solution  of  magnesium  chloride  had  the  greatest  disinte- 
grating effect,  due  to  the  action  of  hydrochloric  acid  produced  by 
the  hydrolysis  of  this  salt. 

A  sodium  sulfate  solution  was  more  harmful  than  a  solution 
of  magnesium  sulfate,  other  conditions  being  equal. 

The  presence  of  sodium  chloride  in  solutions  of  sulfates  of 
sodium  and  magnesium  increased  their  harmful  effect  on  cement. 

A  five  per  cent  solution  of  sodium  sulfate  had  a  stronger 
effect  than  either  the  i  per  cent  or  10  per  cent  solutions. 

The  presence  of  sodium  carbonate  in  solutions  of  the  other 
salts  retards  the  disintegrating  effects. 

Compression  strength  and  tensile  strength  are  not  affected 
in  the  same  degree ;  tensile  strength  decreases  more  rapidly  in  all 
solutions,  even  when  compression  strength  increases. 

Solutions  of  calcium  sulfate  had  no  bad  effects 

Water-proofing  paints  offer  protection  only  for  short  periods 

The  "iron-ore"  cement  resisted  the  action  of  sodium  car- 
bonate-sulfate-chloride  solution ;  the  other  cements  tried  had 
somewhat  lower  tensile  strength. 

The  mixing  of  cement  in  weak  solutions  of  sulfuric  acid, 
di-sodium  phosphate,  magnesium  flouride  and  oxalic  acid  is  of  ad- 
vantage and  increases  the  alkali  resisting  qualities. 


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